Picture this: It’s a Sunday morning and you’ve just finished your 16-mile long run on your marathon training plan.
As you remove your trusty running shoes, you see it—a blood-stained portion of your sock surrounding your big toe. You gasp at the sight, as you were unaware of any trouble, and as you peel away your soiled running sock, you see a black toenail staring back at you.
A black or bruised toenail from running is relatively common, so much so that many runners consider the infliction to be a rite of passage – but they don’t have to be an inevitable part of being a runner.
Knowing the common causes of black toenails in runners can help you take steps to prevent this painful malady, leaving your feet feeling happier and better able to chase true rites of passage for runners like finishing your first marathon.
In this guide, we’re going to look at:
- Why Does Running Cause Bruised Toenails?
- Other Potential Causes Of Black And Bruised Toenails
- Why You Want To Avoid Black Toenails (The Unpleasant Sequela)
- How To Prevent Black Toenails From Running
- How To Treat Bruised Toenails.
Let’s jump in!
Black or Bruised Toenail From Running
A black toenail from running, also called Runner’s Toe, is essentially a bruised toenail.
The most common toenails to be affected by Runner’s Toe are the big toe and the second toe. This is because they are usually the longest toes; therefore, they are most likely to take the brunt of the force or trauma inflicted on the toenail during the running stride.
Though not necessarily a serious running injury, Runner’s Toe can be painful and may potentially interfere with training.
What Causes Bruised Toenails in Runners?
The black or blue color of the bruised toenail with Runner’s Toe is a result of a hematoma or bleeding underneath the toenail.
Rather than resulting from one acute misstep while on the run, bruised toenails are typically due to the accumulated microtraumas your toe experiences during the gait cycle.
How Does Running Cause Bruised Toenails?
There are two phases in the running stride where your toenails can take a tiny beating.
Because you take thousands of strides per run, tiny injuries amass and can ultimately lead to bleeding under your toenail.
When you run, the initial impact of each foot with the ground results in a brief moment where your foot is still moving forward in your shoe, but your shoe itself is planted and not moving.
As your foot slides forward in your running shoe, the toenails may ram into the end of the shoe.
The second point in the running gait cycle where your toenails may take on excessive stress is when you push off to propel the next stride forward. During this motion, your toenails may dig into the footbed of your running shoe, again ramming the ends of your toenails.
Other Causes of Bruised Toenails in Runners
Although the majority of cases of black toenails in runners are due to accumulated microtraumas from the toenails repeatedly colliding with the inside of the shoe, there are other potential causes of bruising, including the following:
- Fungal infection
- Anemia (low iron)
- Heart or kidney disease
If you have concerns about any of the above conditions, it is advisable to consult your healthcare provider.
Blood trapped under the toenail can also be due to a blood blister. These usually result from repetitive friction over damp or sensitive skin. Consider switching to moisture-wicking running socks and ensuring your shoes fit properly, with ample length to accommodate some swelling.
How Do You Know If You Have Runner’s Toe?
If your bruised toenail from running, chances are you have Runner’s Toe. In some cases, the bruised toenail may not be particularly painful, but your toenail may feel tender or more sensitive if it does collide with the end of your shoe.
The most common signs and symptoms of Runner’s Toe include a darkening of the toenail (usually the first or second toe), pain and tenderness, pressure under the nail, and a loosening of the nail from the nail bed. Many runners with bruised toenails end up losing the affected toenail because the nail dies due to the damage to the blood vessels supplying the toenail.
Problems Associated With A Black or Bruised Toenail From Running
Aside from causing discomfort, the bruised toenails characteristic of Runner’s Toe can result in additional problems. The most common sequela is an infection, which can occur if bacteria enters the bloodstream under the toenail.
Signs of an infected toenail include redness, swelling, more intense pain, warmth, and drainage or pus.
To prevent infection, soak the affected foot in warm salt water several times per day and wear clean, dry socks.
How Do Runners Prevent Black Toenails?
As the adage goes, “An ounce of prevention is worth a pound of cure,” and though we love to accumulate medals and accolades as runners, there’s no glory in entering the “black toenail club.” Therefore, it’s important to take the following steps to minimize the chances of getting a bruised toenail from running:
- Trim your toenails: This may be a given, but keeping your toenails neat and trim can prevent them from jutting out beyond your toe where they can then collide with the inside of the shoe. Clip your nails straight across, rather than in a curve, to minimize the risk of ingrown nails.
- Wear properly-fitting running shoes: If you’re a beginner, are prone to running injuries, want to ramp up your volume, or have bruised toenails, consider visiting your local running specialty shop to get fit by running shoe experts. They can analyze your gait, measure your foot, and recommend shoes that optimize your biomechanics. Your running shoes need enough room to accommodate some swelling while you run—particularly if you run in the afternoon or evening, as your feet swell during the day. If your shoes are too tight, your toenails are more apt to ram into the ends of them.
- Tighten your laces: Runner’s Toe is exacerbated by excessive sliding of your foot inside the running shoe. Ensure your laces are adequately tight to hold your foot in place. There are various lacing patterns that you can use, and it’s usually helpful to play around with each to see what works best for you.
- Invest in good running socks: Cushioned running socks with a seamless toe can help absorb force and shield your toenails from jamming into the end of the shoe. Just be careful that your running shoes still fit properly with a thicker, more cushioned sock. You should ideally bring the running socks you want to wear with you when you are fitted for running shoes, or speak to the specialist to get the right socks while you are there.
- Be mindful of your training: Sudden changes in terrain or running volume can cause Runner’s Toe, particularly if you’re running a lot of downhill mileage. Consider varying your terrain if you’re frequently battling bruised toenails.
- Use moleskin or silicone pads: If you have addressed your footwear and trimmed your toenails and still find you’re getting black toenails from running, you can try using adhesive moleskin or silicone pads at the ends of your toes to act as shock-absorbing bumpers inside the running shoe.
How Do You Treat Black Toenails From Running?
In most cases, you don’t have to do much of anything to treat Runner’s Toe or bruised toenail from running. As long as your black toenail isn’t hurting, you should be able to keep running. However, it’s important to not pull the toenail off. Simply keep it trimmed and be sure to wear clean socks. Soak the foot in warm salt water if you are worried about infection.
If the toenail does come off, soaking will become more important. Most medical professionals recommend washing the toe in warm soapy water when the nail falls off, coating it with an antibiotic ointment, and covering it with a sterile dressing.
Follow this same procedure to change the dressing at least once a day, typically after a shower, or anytime it seems dirty or moist. You want to keep the area dry and monitor it for signs of infection. It may take a week or two to heal.